JP2011060037A - Position detector and electrostatic sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic sensor cell, an electrostatic sensor, an electrostatic switch, and a position detector, wherein also noise mixed through a human body can be effectively offset by a simple configuration and noise resistance can be achieved. <P>SOLUTION: In the electrostatic sensor cell, two receiving electrodes have completely symmetrical shapes. Since size adjustment or the like for mounting a sensor on a substrate can be simply executed, a cancel effect of in-phase noise in differential amplification can be displayed effectively at maximum. Further, a land adjacent to one receiving electrode side of one transmitting electrode is formed. Thereby, one transmitting electrode is like an asymmetrical shape when observing it from a differential amplifier. Thereby, in differential amplification, whether a finger approaches or not can be surely detected without losing the cancel effect of the in-phase noise. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a technique suitably applied to a position detection device and an electrostatic sensor.
More specifically, the present invention relates to a technique for reducing noise mixed from a position detection plane and improving finger detection accuracy in an electrostatic position detection device.

There are various input devices that provide position information to a computer. Among them, there is a two-dimensional position information input device (hereinafter referred to as “position detection device”) called a touch panel.
The touch panel is an input device that operates a computer or the like by touching a detection plane with an input body such as a finger or a dedicated pen. A position on the screen is designated by detecting the position touched by a finger or pen, and an instruction is given to the computer.
The touch panel is widely used in PDA (Personal Digital Assistant), bank ATM (Automated Teller Machine), station ticket machines, and the like.

  There are various position information detection techniques employed for touch panels. For example, there are a resistance film method that detects a position by a change in pressure, a capacitance method that detects a position by a change in capacitance of a film on the surface of a detection plane, and the like.

The operation principle of the capacitive position detector will be described.
Electrode wires are wired in a grid pattern on the front and back of a rectangular insulating sheet. An AC signal is applied to the electrode wire on one surface, and current is detected from the electrode wire on the back surface via the insulating sheet. Since a capacitor is formed through an insulating sheet at the intersection of the electrode wires wired in a grid pattern, a current flows when an AC voltage is applied to both electrode wires.
At this time, when the frequency of the AC signal is set to 200 kHz, for example, and a human finger is brought close to one electrode line, a phenomenon occurs in which a part of the electric charge stored in the capacitor by the AC voltage is absorbed by the human body. A change in the capacitance of the capacitor caused by a part of the electric charge absorbed by the human body is detected through a current flowing through the capacitor. However, since the current that can be detected is extremely weak, it is converted into a voltage signal through a current-voltage conversion circuit using a known operational amplifier, and voltage amplification is performed.

Even a signal amplified by current-voltage conversion processing is originally a weak current, and therefore noise around the apparatus is mixed into the detected signal. Therefore, noise canceling using a known differential amplification is performed.
If two electrode lines that are spaced enough to detect the finger are selected from the electrode lines on the receiving side, and each electrode line on the receiving side is connected to the differential amplifier, the finger is close to one of the electrode lines. Since the finger is not approaching the other electrode line, the presence of the finger can be detected by taking the difference between the signals. Further, noise components mixed in both electrode lines in the same phase are canceled by the differential amplifier.
The prior art relating to the applicant's invention is shown in Patent Document 1.

JP-A-10-020992

By the way, in general, when an electronic device having a function of receiving electromagnetic waves or the like is used indoors, a hum noise or the like of a surrounding power line is mixed into the electronic device through a human body.
In the case of such noise mixed through the human body, there is a problem that the configuration of the receiving electrode line as described above cannot be canceled by the differential amplifier. As a result, there arises a problem that the position of the finger cannot be correctly detected or the position detecting device itself malfunctions.

  The present invention has been made in view of the above points, and provides a noise-resistant electrostatic sensor capable of effectively canceling out noise mixed through a human body with a simple configuration, and a position detection device using the same. For the purpose.

  In order to solve the above-described problem, the position detection device according to the present invention includes a plurality of conductor patterns having a predetermined number of land portions arranged in the first direction and the second crossing the first direction. A sensor in which at least two conductor patterns in the direction and in the vicinity of the land portion are close to each other and electrically insulated from the conductor pattern having the land portion, and a conductor pattern arranged in the first direction is predetermined. Detecting signal having a signal supply circuit for supplying the signal and a differential amplifier circuit for generating a differential signal of the two signals supplied from two conductor patterns arranged in the second direction The position of the indicator on the sensor is obtained based on a change in electrostatic coupling between the conductor pattern arranged in the first direction and the conductor arranged in the second direction. It is a thing.

  An electrostatic sensor was configured by alternately arranging conductor patterns having a predetermined number of land portions serving as transmission electrodes on the sensor substrate, and providing two conductor patterns serving as reception electrodes orthogonal to the conductor patterns. This electrostatic sensor forms a state in which signals are balanced in a normal state by alternately combining conductor pattern shapes that output unbalanced signals. The position detection device of the present invention uses this electrostatic sensor. This makes it possible to provide a practical position detection device that has a simple circuit configuration, is resistant to noise, and has a high scanning speed.

  According to the present invention, it is possible to provide a noise-resistant electrostatic sensor capable of effectively canceling out noise mixed through a human body with a simple configuration, and a position detection device using the same.

It is an external appearance perspective view of the electrostatic sensor cell which is an example of 1st embodiment of this invention. It is the external view which looked at the electrostatic sensor cell which is an example of 1st embodiment of this invention from the side and the top. It is a block diagram of an electrostatic switch which is an example of a first embodiment of the present invention. It is a figure explaining the principle of an electrostatic switch. It is the figure explaining the principle of an electrostatic switch, and an equivalent circuit. It is a wave form diagram for demonstrating operation | movement of an electrostatic switch. It is a block diagram of the electrostatic switch which is an example of 2nd embodiment of this invention. It is a wave form diagram for demonstrating operation | movement of an electrostatic switch. It is an external appearance perspective view of the position detection apparatus which is an example of 3rd embodiment of this invention. It is a block diagram of a position detection apparatus. It is a block diagram of a transmission switch part. It is a block diagram of a reception switch part. It is a block diagram of an analog signal processing unit. It is a block diagram of a control part. It is an equivalent circuit diagram for demonstrating the principle of a position detection apparatus. It is a wave form diagram for demonstrating operation | movement of a position detection apparatus. It is explanatory drawing explaining the principle of operation which detects a finger | toe. It is explanatory drawing explaining the operation principle which detects the finger | toe of the position detection apparatus which is an example of 4th embodiment of this invention. It is the schematic which shows an example of the wiring pattern of a sensor board | substrate. It is the schematic which shows an example of the wiring pattern of a sensor board | substrate.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

[Electrostatic switch consisting of a single electrostatic sensor cell]
First, in order to explain the principle of the invention, a single electrostatic sensor cell and an electrostatic switch constructed using the same will be described.
The electrostatic sensor cell will be described with reference to FIGS. Here, FIG. 1 is a perspective view of the electrostatic sensor cell of the present invention, FIG. 2A is a sectional view of the electrostatic sensor cell of the present invention, and FIG. 2B is a top view of the electrostatic sensor cell of the present invention.
First, a schematic configuration of the electrostatic sensor cell will be described. As shown in FIGS. 1 and 2, the electrostatic sensor cell 101 includes a substantially flat insulating sheet 202, a transmission conductor 102, a plurality of reception electrodes 103, and a protection sheet 203.

  As shown in FIG. 2A, the transmission conductor 102 is provided on one surface of the insulating sheet 202. As shown in FIG. 1, the transmission conductor 102 includes a main body portion 102a made of a conductor and a land portion 102b. The main body 102a has a predetermined width and is formed in the X-axis direction (first direction) of the electrostatic sensor cell 101. The land portion 102b is provided in the main body portion 102a, and is formed, for example, in the Y-axis direction of the electrostatic sensor cell 101 (a second direction that is a direction orthogonal to the first direction).

The reception electrode 103 includes a pair of first and second reception conductors 103a and 103b made of a conductor provided on the other surface of the insulating sheet 202. The first and second receiving conductors 103a and 103b are provided substantially parallel to each other, and are formed in the Y-axis direction.
The protective sheet 203 is an insulator formed in a substantially flat plate shape for preventing direct contact between a human finger and the receiving electrode 103. The protective sheet 203 is provided so as to cover the entire other surface of the electrostatic sensor cell 101.

FIG. 3 is a block diagram of the electrostatic switch.
As shown in FIG. 3, the electrostatic switch 301 functions as a switch by connecting a predetermined circuit to the electrostatic sensor cell 101. When the electrostatic switch 301 brings a finger close to the area P314 surrounded by the dotted line of the electrostatic sensor cell 101, the logic output is inverted.
The signal source 302 generates a periodic signal having a constant voltage and a constant frequency, such as an alternating current or a pulse signal.
A signal emitted from the signal source 302 is supplied to the transmission conductor 102.

On the other hand, resistors R303 and R304 and operational amplifiers 305 and 306 are connected to the two receiving electrodes of the first receiving conductor 103a and the second receiving conductor 103b, respectively. The resistor R303 and the operational amplifier 305, and the resistor R304 and the operational amplifier 306 constitute a known current-voltage conversion circuit, respectively.
The output signals of the operational amplifiers 305 and 306 are input to the differential amplifier 307, respectively.
The electrostatic sensor unit 308 including the signal source 302, the electrostatic sensor cell 101, the resistor R 303 and the operational amplifier 305, the resistor R 304 and the operational amplifier 306, and the differential amplifier 307 is the basic configuration of the electrostatic switch 301.

The output signal of the differential amplifier 307 is a very weak AC signal. As it is, it does not function as a switch. Therefore, the function as a switch is realized in the subsequent circuit.
The multiplier 309 is a circuit that performs analog multiplication processing on the output signal of the differential amplifier 307 and the output signal of the signal source 302. Multiplier 309 converts the negative period portion of the signal into a positive signal, resulting in a signal equal to the full wave rectified signal. The multiplier 309 may be a synchronous detector.
When the output signal of the multiplier 309 is supplied to a low-pass filter (LPF) 310, the high-frequency component is removed and smoothed.
The signal smoothed by the LPF 310 is compared with a reference voltage by a comparator 311. A logical value (output voltage level) that is the comparison result is output as a switch output.

  An integrator may be used instead of the LPF 310. When using an integrator, it is necessary to periodically reset. Further, when using an integrator, instead of performing voltage comparison by the comparator 311, it may be converted to a digital value by an A / D converter to perform numerical comparison. The sampling timing of the A / D converter is preferably performed immediately before the integrator is reset.

As described above, the circuit configuration subsequent to the electrostatic sensor unit 308 can be variously modified. On the other hand, the circuit configuration of the electrostatic sensor unit 308 hardly deviates from the configuration of the signal source 302, the electrostatic sensor cell 101, the resistor R303 and the operational amplifier 305, the resistor R304, and the differential amplifier 307 described above. In particular, since it is necessary for the transmission conductor 102 of the electrostatic sensor cell 101 to be asymmetric in order to detect a change in capacitance of the electrostatic sensor cell 101, the differential amplifier 307 is an essential component.
Therefore, the electrostatic sensor unit 308 includes two symmetrical receiving electrodes, an electrostatic sensor cell 101 including one asymmetrical transmitting conductor 102, and a differential amplifier 307 connected to the two receiving electrodes. It is essential.

  The principle and equivalent circuit of the electrostatic switch 301 will be described with reference to FIGS. 4A and 4B are diagrams for explaining the principle of the electrostatic switch 301. FIG. 5A, 5B, 5C, 5D, and 5E are diagrams for explaining the principle of the electrostatic switch 301 and an equivalent circuit. FIG. 4A is a view of a state in which a finger is close to the electrostatic sensor cell 101 as viewed from above. FIG. 4B is a side view of a state in which a finger is close to the electrostatic sensor cell 101. FIG. 5A is a view of the electrostatic sensor cell 101 as seen from above, which is the same as FIG. However, the finger 402 is omitted. FIG. 5B is a view from the side of the electrostatic sensor cell 101 in a state where the finger 402 is not in proximity to the electrostatic sensor cell 101, as in FIG. FIG. 5C is an equivalent circuit of FIG. However, the current-voltage conversion circuit is omitted. FIG. 5D is a view from the side of the electrostatic sensor cell 101 in the state where the finger 402 is close to the electrostatic sensor cell 101, as in FIG. 4C. FIG. 5E is an equivalent circuit of FIG. However, the current-voltage conversion circuit is omitted.

As shown in FIGS. 4A and 4B, the finger 402 extends from the land portion 102 b of the transmission conductor 102 to the two reception electrodes of the first reception conductor 103 a and the second reception conductor 103 b of the electrostatic sensor cell 101. Cover to cover.
The human body can be regarded as equivalent to a conductor when viewed electrically. Therefore, when the finger 402 is regarded as a conductor and FIG. 4B is viewed electrically, the transmission conductor 102, the first reception conductor 103 a, the second reception conductor 103 b, and the finger 402, FIG. It can be considered that a capacitor as shown in FIG.
When there is no finger 402, it can be considered that a capacitor as shown in FIG. 5B is formed.

Consider the states of FIGS. 5B and 5C.
In a state where the finger 402 is not in proximity to the electrostatic sensor cell 101, the land portion 102b of the transmission conductor 102 faces the longitudinal direction of the second reception conductor 103b, and thus the land portion 102b and the second reception conductor 103b. A capacitor Cpa is formed in a portion facing the longitudinal direction.
On the other hand, the length of the location where the first receiving conductor 103a and the transmitting conductor 102 are opposed is shorter than the portion where the land portion 102b and the second receiving conductor 103b are opposed to the hand direction. A capacitor Cma having a capacitance smaller than that of the capacitor Cpa is formed at a portion where the transmission conductor 102 and the first reception conductor 103a are opposed to each other in the longitudinal direction.

As described with reference to FIG. 3, the differential amplifier 307 includes a voltage corresponding to a current flowing through the second receiving conductor 103b that is a plus-side receiving electrode and a current flowing through the first receiving conductor 103a that is a minus-side receiving electrode. Outputs the difference from the voltage according to.
In FIG. 5C, the current flowing through the second receiving conductor 103b is the current flowing through the combined capacitance of the capacitors Cp1 and Cp2. Similarly, the current flowing through the first receiving conductor 103a is the current flowing through the combined capacitance of the capacitors Cm1 and Cm2.
As is well known, the capacitance of a capacitor is inversely proportional to the distance between adjacent electrodes and proportional to the area of electrodes overlapping.

As shown in FIG. 5A, the land portion 102b of the transmission conductor 102 is close to the second reception conductor 103b. For this reason, compared with the 1st receiving conductor 103a, as for the 2nd receiving conductor 103b, the electrostatic capacitance has increased in the location where the longitudinal direction and the edge | side of the land part 102b are adjoining. That is, in a state where the finger 402 is not in proximity, the relationship Cp2> Cm2 is established.
Since the current flowing through the capacitor is inversely proportional to the capacitance of the capacitor, a detection result biased toward the positive terminal of the differential amplifier 307 is obtained in FIG.

On the other hand, consider the equivalent circuit in FIG. 5D and FIG. In FIG. 5E, Cf is the capacitance of the human body itself.
In FIG. 5E, the current flowing through the second receiving conductor 103b is the sum of the current flowing through the capacitor Cp1 and the current flowing through Cpb. The current flowing through Cpb is calculated from the combined capacitance of Cpa and Cma (Cpa + Cma) and the combined capacitance of Cpb, Cmb, and Cf (Cpb + Cmb + Cf).
The combined capacitance of the capacitor Cp1 and Cpa, Cma, Cpb, Cmb, and Cf derived from the above consideration is expressed by the following equation.

Similarly, the current flowing through the first receiving conductor 103a is a combined capacity of the capacitor Cm1, Cpa, Cma, and Cmb, Cpb, and Cf.
The combined capacitance of the capacitor Cm1 and Cma, Cpa, Cmb, Cpb, and Cf, which is derived from the above consideration, is as follows.

Next, the combined capacity of the above two equations is subtracted. The capacitance value obtained by subtraction determines the current value finally obtained by the differential amplifier 307.
Considering that the sizes of the second receiving conductor 103b and the first receiving conductor 103a are exactly the same in size, height, etc.
Cp1≈Cm1
Cpb ≒ Cmb
Can lead.
Then, the result of the equation becomes almost zero as follows.

  What can be said from the above consideration is that when the finger 402 as a conductor covers the electrostatic sensor cell 101, there is almost no difference in capacitance between the plus-side receiving electrode and the minus-side receiving electrode.

  6A, 6B, 6C, 6D, 6E, 6G, and 6H are waveform diagrams for explaining the operation of the electrostatic switch 301. FIG. . This is a consideration of various waveforms based on FIG. In FIG. 6, the first receiving conductor 103a is read as a minus receiving electrode, and the second receiving conductor 103b is read as a plus receiving electrode for easy understanding. FIG. 6A shows a waveform of a current that appears at the plus-side receiving electrode in a state where the finger 402 is not in proximity to the electrostatic sensor cell 101. FIG. 6B is a waveform of a current that appears at the negative receiving electrode in a state where the finger 402 is not in proximity to the electrostatic sensor cell 101. FIG. 6C shows a voltage waveform that appears in the differential amplifier 307 in a state where the finger 402 is not in proximity to the electrostatic sensor cell 101. FIG. 6D shows a waveform of a current that appears at the plus-side receiving electrode when the finger 402 is close to the electrostatic sensor cell 101. FIG. 6E shows a waveform of a current that appears at the negative receiving electrode in a state where the finger 402 is close to the electrostatic sensor cell 101. FIG. 6F shows a voltage waveform that appears in the differential amplifier 307 when the finger 402 is close to the electrostatic sensor cell 101. FIG. 6G shows a voltage waveform that appears in the multiplier 309 when the finger 402 is not in proximity to the electrostatic sensor cell 101. FIG. 6H shows a voltage waveform that appears in the multiplier 309 when the finger 402 is close to the electrostatic sensor cell 101.

An operation of the electrostatic sensor unit 308 in a state where the finger 402 is not in proximity to the electrostatic sensor cell 101 will be described.
Comparing FIGS. 6A and 6B, the amplitude of the waveform of the current that appears at the plus-side receiving electrode is larger than the amplitude of the waveform of the current that appears at the minus-side receiving electrode because of the relationship Cp2> Cm2. .
Therefore, the output signal of the differential amplifier 307, which is the result of subtracting the signal having the waveform (b) from the signal having the waveform shown in FIG. 6 (a), is as shown in FIG. 6 (c).

Next, the operation of the electrostatic sensor unit 308 when the finger 402 is close to the electrostatic sensor cell 101 will be described.
When the finger 402 comes close to the electrostatic sensor cell 101, the capacitance of the electrostatic sensor cell 101 as viewed from the plus side receiving electrode and the minus side receiving electrode increases. For this reason, the amplitudes of the waveforms in FIGS. 6D and 6E are larger than those in FIGS. 6A and 6B, respectively. Further, as described in the above formula, the amplitudes of the waveforms in FIGS. 6D and 6E are almost the same.
Therefore, the output signal of the differential amplifier 307, which is the result of subtracting the signal of the waveform (e) from the signal of the waveform of FIG. 6 (d), is as shown in FIG. 6 (f). Compared with the waveform of FIG. 6C, the amplitude is very small.

When the signal of FIG. 6C is input to the multiplier 309, a pulsating flow having a predetermined amplitude is obtained as shown in FIG. When the signal shown in FIG. 6 (f) is input to the multiplier 309, a pulsating current having a smaller amplitude than that shown in FIG. 6 (g) is obtained as shown in FIG. 6 (h).
That is, when the finger 402 approaches the electrostatic sensor cell 101, the amplitude of the output signal decreases. The electrostatic switch 301 recognizes the change in the amplitude of the output signal.

[Electrostatic switch composed of two electrostatic sensor cells 101]
Next, an electrostatic switch constituted by using two single electrostatic sensor cells described above in combination with each other will be described.
FIG. 7 is a block diagram of the electrostatic switch. In addition, the same code | symbol is attached | subjected to the same component as FIG. 3 among the components shown in FIG.
The electrostatic switch 701 in FIG. 7 has the same circuit configuration as the electrostatic switch 301 shown in FIG. The only difference is that two electrostatic sensor cells 101 are combined. Hereinafter, one in which two electrostatic sensor cells 101 are alternately combined is referred to as an electrostatic sensor unit 702. The electrostatic sensor unit 702 is an assembly in which two electrostatic sensor cells 101 having a common first receiving conductor 103a and second receiving conductor 103b are alternately combined.

Below the two reception electrodes of the first reception conductor 103a and the second reception conductor 103b, the two transmission electrodes of the first transmission electrode 703 and the second transmission electrode 704 are staggered, and They are arranged in an orthogonal direction.
When detecting the presence of the finger 402, the finger 402 is brought close to a region P705 surrounded by a dotted line. The region P705 is a region that covers one of the two electrostatic sensor cells 101 constituting the electrostatic sensor unit 702.

  FIGS. 8A, 8B, 8C, 8D, and 8E are waveform diagrams for explaining the operation of the electrostatic switch 701. FIG. FIG. 8A shows a voltage waveform that appears in the differential amplifier 307 when it is assumed that the signal source 302 is connected only to the first transmission electrode 703 in a state where the finger 402 is not in proximity to the region P705. is there. FIG. 8B shows a voltage waveform appearing in the differential amplifier 307 when it is assumed that the signal source 302 is connected only to the second transmission electrode 704 in a state where the finger 402 is not in proximity to the region P705. is there. FIG. 8C shows the differential amplifier 307 when the signal source 302 is connected to the first transmission electrode 703 and the second transmission electrode 704 in a state where the finger 402 is not close to the region P705. This is the voltage waveform that appears. FIG. 8D shows a voltage waveform that appears in the differential amplifier 307 when it is assumed that the signal source 302 is connected only to the first transmission electrode 703 in a state where the finger 402 is close to the region P705. is there. FIG. 8E shows the differential amplifier 307 when the signal source 302 is connected to the first transmission electrode 703 and the second transmission electrode 704 in a state where the finger 402 is close to the region P705. This is the voltage waveform that appears.

The waveform in FIG. 8A is the same as the waveform in FIG. That is, it is an output signal of the differential amplifier 307 in a state where the finger 402 is not approaching the region P705 and there is only one electrostatic sensor cell 101.
The waveform of FIG. 8B is 180 ° out of phase with the waveform of FIG. This is because the direction of the second transmission electrode 704 is opposite to the first transmission electrode 703.
FIG. 8C shows the result of synthesizing the waveforms shown in FIGS. 8A and 8B in which the amplitude is the same and the phase is inverted by 180 °. That is, in the state where the finger 402 is not approaching the region P705, the signals obtained from the alternately arranged electrostatic sensor cells 101 cancel each other and become zero.

On the other hand, the waveform in FIG. 8D is the same as the waveform in FIG. That is, it is an output signal of the differential amplifier 307 in a state where the finger 402 is approaching the region P705.
FIG. 8 (e) shows the result of synthesizing the waveforms of FIGS. 8 (d) and 8 (b). That is, in a state where the finger 402 is approaching the region P705, signals obtained from the electrostatic sensor cells 101 arranged alternately are not completely canceled because one of the amplitudes is reduced, and the signal from the differential amplifier 307 Appears.

In the first embodiment described above, a phenomenon is used in which the finger 402 covers the electrostatic sensor cell 101 so that the difference between the electrostatic capacity appearing on the positive receiving electrode and the electrostatic capacity appearing on the negative receiving electrode is almost eliminated. An electrostatic switch has been disclosed.
However, as shown in FIG. 6 (i), even if the finger 402 is actually placed on the electrostatic sensor cell 101, the difference in capacitance is not completely zero. There are some differences due to various factors. There is also room for error due to noise.

  The performance required for the switch is that the on state and the off state are clear. That is, it is desirable to obtain a completely zero state in either the state where the finger 402 is close or the state where the finger 402 is not close. Therefore, another transmission conductor 102 formed asymmetrically is provided in the opposite direction. That is, another electrostatic sensor cell that is symmetrical to the electrostatic sensor cell of the first embodiment is combined. Then, the mutually asymmetric signals cancel each other, and a zero state without the finger 402 can be obtained from the differential amplifier 307.

[Position detection device using electrostatic sensor cell]
A position detection device can be realized by configuring a sensor substrate in which a large number of electrostatic sensor units 702 each formed by alternately combining asymmetrical electrostatic sensor cells 101 are developed on a plane.
The first embodiment and the second embodiment described above are also explanations of the operation principle of the position detection device of the third embodiment.

A schematic configuration of a position detection apparatus to which the present invention is applied will be described with reference to FIG. FIG. 9 is a perspective view showing a position detection apparatus to which the present invention is applied.
A position detection device 901 according to an embodiment of the present invention (hereinafter referred to as “this example”) is connected to an external device (not shown) such as a personal computer or a PDA (Personal Digital Assistant), and inputs from these external devices. It is used as a device. Although not specifically illustrated and described, the position detection device 901 may be built in a personal computer or the like.

A position detection device 901 according to an embodiment of the present invention (hereinafter referred to as “this example”) is connected to an external device (not shown) such as a personal computer or a PDA (Personal Digital Assistant), thereby It is used as an input device. Although not specifically illustrated and described, the position detection device 901 may be built in a personal computer or the like.
The position detection device 901 includes a position detection plane 902 that detects a human body (finger) that is an indicator and a dedicated pen (not shown), a housing that forms a hollow thin substantially rectangular parallelepiped having the position detection plane 902, and the like. It is composed of
Then, the user performs input of characters and drawings by pointing operation and various operations on the position detection plane 902 via a human body (finger) or a dedicated pen (not shown) as an indicator.

  Immediately below the position detection plane 902 of the position detection device 901, an electrostatic sensor described later in FIG. 10 is embedded.

Next, the circuit configuration of the position detection apparatus of the present invention will be described with reference to FIG.
The position detection device 901 includes an electrostatic sensor 1002, a transmission switch unit 1003, a reception switch unit 1004, an analog signal processing unit 1005, an A / D converter 1006, and a control unit 1007.
The electrostatic sensor 1002 is a sensor configured by providing a plurality of transmission conductors 102 and reception electrodes 103 made of a conductor on both surfaces of a substantially flat insulator. The plurality of transmission conductors 102 are connected to the transmission switch unit 1003, and the plurality of reception electrodes 103 are connected to the reception switch unit 1004.

The reception switch unit 1004 is a switch for selecting the reception electrode 103 to be detected. The reception switch unit 1004 receives a control signal from a control unit 1007 to be described later, and selects an arbitrary reception electrode 103 based on the control signal. An analog signal processing unit 1005 is connected to the output terminal of the reception switch unit 1004. The output signal of the reception switch unit 1004 is supplied to the analog signal processing unit 1005.
The analog signal processing unit 1005 is for performing predetermined processing on the output signal from the reception switch unit 1004. The signal input to the analog signal processing unit 1005 is subjected to predetermined processing and output. This signal processing will be described later.

The output signal output from the analog signal processing unit 1005 is supplied to the A / D converter 1006, and the voltage of the input signal is converted into digital data.
The output data of the A / D converter 1006 is supplied to a control unit 1007 composed of, for example, a microcomputer.
The control unit 1007 controls the transmission switch unit 1003, the reception switch unit 1004, and the A / D converter 1006, and the presence / absence of the finger 402 on the electrostatic sensor 1002 based on the output data of the A / D converter 1006 And information indicating its position are output.

Next, details of the electrostatic sensor 1002 will be described with reference to FIG. 10 and FIGS. 1 and 2.
First, a schematic configuration of the electrostatic sensor 1002 will be described. As shown in FIGS. 1 and 2A, the electrostatic sensor 1002 includes a substantially flat insulating sheet 202, a plurality of transmission conductors 102 provided substantially parallel to each other, a plurality of reception electrodes 103, and a protection And a sheet 203. As can be seen with reference to FIG. 10 and FIGS. 1 and 2, the electrostatic sensor 1002 is an assembly of electrostatic sensor cells. The electrostatic sensor 1002 is formed of a known glass epoxy substrate or a flexible printed substrate.

  As shown in FIG. 2A, the transmission conductor 102 is provided on one surface of the insulating sheet 202. As can be seen with reference to FIGS. 1 and 10, the transmission conductor 102 includes a main body portion 102a made of a conductor and a plurality of land portions 102b. The main body 102a has a predetermined width and is formed by extending in the X-axis direction (first direction) of the electrostatic sensor 1002. The land portion 102b is provided in the main body portion 102a, and is formed, for example, by extending in the X-axis direction of the electrostatic sensor 1002 (a second direction that is a direction orthogonal to the first direction). And as shown in FIG. 10, this land part 102b is provided at equal intervals in the extending | stretching direction (Y-axis direction) of the main-body part 102a.

The receiving electrode 103 is composed of a pair of first and second receiving conductors 103 a and 103 b made of a conductor provided on the other surface of the insulating sheet 102. The first and second receiving conductors 103a and 103b are provided substantially parallel to each other, and are formed by extending in the Y-axis direction.
The protective sheet 203 is an insulator formed in a substantially flat plate shape for preventing direct contact between a human finger and the receiving electrode 103. This protective sheet 203 is provided so as to cover the entire other surface of the electrostatic sensor 1002.

  Next, the positional relationship between the transmission conductor 102 and the reception electrode 103 constituting the electrostatic sensor 1002 will be described in detail with reference to FIGS. The plurality of transmission conductors 102 provided on one surface of the insulating sheet 202 are disposed substantially parallel to each other in the Y-axis direction. As can be seen with reference to FIGS. 1 and 10, the transmission conductor 102 includes a land portion 102b of one transmission conductor 102 and two transmission conductors 102 adjacent to the transmission conductor 102 in the Y-axis direction. The main body portions 102a of the two adjacent transmission conductors 102 are provided adjacent to each other. That is, when attention is paid to any one land portion 102b of the transmission conductor 102, the main body portions 102a and the land portions 102b are alternately arranged in the Y-axis direction.

  One receiving electrode composed of a pair of receiving conductors 103 a and 103 b provided on the other surface of the insulating sheet 102 is provided so as to be positioned between the land portions 102 b of the two adjacent transmitting conductors 102. That is, the two reception conductors 103 a and 103 b are arranged orthogonal to the main body portion 102 a of the transmission conductor 102. Here, paying attention to a pair of reception conductors 103a and 103b and an arbitrary transmission conductor 102 constituting an arbitrary one reception electrode 103, the pair of reception conductors 103a and 103b and the transmission conductor 102 are the transmission conductors. The first receiving conductor 103a and one land portion 102b of the transmitting conductor 102 are close to each other, and the other second receiving conductor 103b and another land portion 102b are close to each other. Will do.

Next, the transmission switch unit 1003 will be described with reference to FIG. The transmission switch unit 1003 includes a shift register 1102 and a plurality of NOT gates 1103.
The shift register 1102 is composed of the same number of bit cells 1102 a as the transmission conductors 102. Each bit cell 1102a is connected to each transmission conductor 102 via a NOT gate 1103. The shift register 1102 receives a clock pulse, a reset pulse, and transmission-side switch data from the control unit 1007.

  Next, the configuration of the reception switch unit 1004 will be described with reference to FIG. The reception switch unit 1004 includes a plurality of analog switches 1203 and a shift register 1202.

The analog switch 1203 includes switches 1203a and 1203b made up of a pair of analog multiplexers. The reception switch unit 1004 is provided with the same number of analog switches 1203 as the reception electrodes 103. The analog switch 1203 receives a control signal from a shift register 1202, which will be described later, and performs an on / off operation based on the control signal.
The input terminals of the pair of switches 1203a and 1203b constituting the analog switch 1203 are connected to the receiving conductors 103a and 103b, respectively, and the output terminals are connected to the plus side output line 1204 or the minus side output line 1205.

  The shift register 1202 includes the same number of bit cells 1202 a as the reception electrodes 103. Each bit cell 1202a is connected to an analog switch 1203. The shift register 1202 receives a clock pulse, a reset pulse, and a data signal output from the control unit 1007.

Next, the analog signal processing unit 1105 will be described with reference to FIG.
The analog signal processing unit 1105 includes two current-voltage conversion units 1105a and 1105b, a differential amplifier 307, and a low-pass filter 1302 (hereinafter abbreviated as LPF).
The current-voltage conversion unit 1105a includes a resistor R303 and an operational amplifier 305. Similarly, the current-voltage conversion unit 1105b includes a resistor R304 and an operational amplifier 306. These current / voltage converters 1105a and 1105b are connected to the minus-side output line 1205 and the plus-side output line 1206, respectively, and convert and amplify the current output from these output lines to a subsequent differential amplifier. To 307.

The differential amplifier 307 is connected to the output terminals of the current / voltage converters 1105a and 1106b, and differentially amplifies and outputs the voltage signals output from these current / voltage converters 1105a and 1106b.
The signal output from the differential amplifier 307 is output to the A / D converter 1006 via the LPF 1302.

Next, the configuration and operation of the control unit 1007 will be described with reference to FIG.
The control unit 1007 includes a clock generation unit 1402, a transmission side address counter 1403, a transmission side switch data generation unit 1404, a reception side address counter 1405, a reception side switch data generation unit 1406, a buffer memory 1407, a center of gravity. And an arithmetic unit 1408.

The clock generation unit 1402 generates a clock pulse having a predetermined frequency to be supplied to the transmission conductor 102. This clock pulse is supplied to the subsequent transmission side address counter 1403 and the transmission side switch data generation unit 1404. The clock pulse is supplied to the A / D converter 1006 and used as a timing pulse of the A / D converter circuit, and is also supplied to the transmission conductor 102 via the transmission switch unit 1003 and used as a transmission signal.
The transmission clock pulse is supplied to the transmission side address counter 1403 and the transmission side switch data generation unit 1404.

  The transmission-side address counter 1403 is a loop counter that counts the number of transmission electrodes 1008 as the maximum number. The output pulse signal at the overflow address terminal of the transmission side address counter 1403 is output as a reset pulse for the transmission side switch data generation unit 1404 and the transmission switch unit 1003. The reset pulse is supplied as a clock pulse for the reception-side address counter 1405, the reception-side switch data generation unit 1406, and the reception switch unit 1004. Hereinafter, this clock pulse is referred to as a reception clock pulse.

  The receiving side address counter 1405 is a loop counter that counts the number of sets of receiving electrodes as the maximum number. An output signal of the overflow address terminal of the reception side address counter 1405 is output as a reset pulse of the reception side switch data generation unit 1406 and the reception switch unit 1004.

The transmission-side switch data generation unit 1404 is activated by a reset pulse (reception clock pulse) and a transmission clock pulse generated by the transmission-side address counter 1403, generates transmission-side switch data, and sends it to the transmission switch unit 1003.
This transmission-side switch data is a rectangular wave signal that is an integral multiple of a half cycle of the transmission clock pulse. The transmission-side switch data generation unit 1404 counts a predetermined number of up and down edges of the transmission clock pulse from the timing when the reset pulse is input, and maintains the logic true (high potential) state during that time. When the count value reaches the predetermined number, it returns to the logic false (low potential) state, and thereafter the logic false state is maintained until a reset pulse is input again.
The “predetermined number” of the up and down edges is “4”.

The reception-side switch data generation unit 1406 is activated by the reset pulse and reception clock pulse generated by the reception-side address counter 1405, generates reception-side switch data, and sends it to the reception switch unit 1004.
This reception-side switch data is a rectangular wave signal that is an integral multiple of a half cycle of the reception clock pulse. The reception-side switch data generation unit 1406 counts a predetermined number of up and down edges of the reception clock pulse from the timing when the reset pulse is input, and maintains the logic true (high potential) state during that time. When the count value reaches the predetermined number, it returns to the logic false (low potential) state, and thereafter the logic false state is maintained until a reset pulse is input again.
The “predetermined number” of the up and down edges is “2”.

The transmission address data output from the transmission side address counter 1403 and the reception address data output from the reception side address counter 1405 are supplied to the buffer memory 1407. A buffer memory 1407 is a memory for temporarily storing output data of the A / D converter 1006. The buffer memory 1407 is supplied with the output data of the A / D converter 1006 and stores the output data of the A / D converter 1006 at an address defined by the transmission address data and the reception address data.
The center-of-gravity calculation unit 1408 reads the data stored in the buffer memory 1407, performs center-of-gravity calculation, and outputs the presence / absence of a finger and position information.

Next, the operation principle of the position detection device 901 will be described with reference to FIG. FIG. 15 is an equivalent circuit for explaining the principle of the position detection device 901. As shown in FIG. 15, the transmission switch unit 1003 of the position detection device 901 is equivalent to a rectangular wave signal source 1502. Hereinafter, an arbitrary first transmitting electrode 703, a second transmitting electrode 704 adjacent to the first transmitting electrode 703, and a receiving electrode 103 made up of optional first and second receiving conductors 103a and 103b have a finger 402 and a region P1503. A case where they are close to each other will be described as an example.
The rectangular wave signal source 1502 is a virtual circuit that equivalently represents the transmission switch unit 1003. As the name suggests, the rectangular wave signal source 1502 generates a rectangular wave signal.

  16 (a), (b), (c), (d), (e), (f), (g), (h), (i), (j), (k) and (l) are FIG. 16 is a waveform diagram based on the equivalent circuit diagram of FIG. 15 for explaining the operation of the position detection device 901. A state where the finger 402 is approaching the region P1503 in FIG. 15 and a state where the finger 402 is not approaching are assumed. FIG. 16A shows a voltage waveform output from the rectangular wave signal source 1502. FIG. 16B shows a waveform of a current that appears at the plus-side receiving electrode when it is assumed that the signal source is connected only to the first transmitting electrode 703 in a state where the finger 402 is not in proximity to the region P1503. is there. FIG. 16C shows a waveform of a current that appears at the minus-side receiving electrode when it is assumed that the signal source is connected only to the first transmitting electrode 703 in a state where the finger 402 is not in proximity to the region P1503. is there. FIG. 16D shows a voltage waveform appearing in the differential amplifier 307 when it is assumed that the signal source is connected only to the first transmission electrode 703 in a state where the finger 402 is not in proximity to the region P1503. . FIG. 16E shows a waveform of a current that appears at the plus-side receiving electrode when it is assumed that a signal source is connected only to the second transmitting electrode 704 in a state where the finger 402 is not in proximity to the region P1503. is there. FIG. 16F shows a waveform of a current appearing on the negative receiving electrode when it is assumed that a signal source is connected only to the second transmitting electrode 704 in a state where the finger 402 is not in proximity to the region P1503. is there. FIG. 16G shows a voltage waveform appearing in the differential amplifier 307 when it is assumed that the signal source is connected only to the second transmission electrode 704 in a state where the finger 402 is not in proximity to the region P1503. . FIG. 16H appears in the differential amplifier 307 in a state where the finger 402 is not close to the region P1503 and a signal source is connected to the first transmission electrode 703 and the second transmission electrode 704. It is a voltage waveform. FIG. 16I shows a waveform of a current that appears at the plus-side receiving electrode when it is assumed that the signal source is connected only to the first transmitting electrode 703 in a state where the finger 402 is close to the region P1503. is there. FIG. 16J shows the waveform of the current appearing on the negative receiving electrode when it is assumed that the signal source is connected only to the first transmitting electrode 703 in a state where the finger 402 is close to the region P1503. is there. FIG. 16K shows a voltage waveform appearing in the differential amplifier 307 when it is assumed that a signal source is connected only to the first transmission electrode 703 in a state where the finger 402 is close to the region P1503. . FIG. 16L appears in the differential amplifier 307 in a state where the finger 402 is close to the region P1503 and a signal source is connected to the first transmission electrode 703 and the second transmission electrode 704. It is a voltage waveform.

As shown in FIG. 16A, the rectangular wave voltage source generates a signal having a waveform similar to a step function, which changes from a low potential to a high potential.
First, consider the waveforms that appear in the electrostatic sensor cell 101 and the differential amplifier 307 with the finger 402 not approaching the region P1503.
Attention is paid to the first transmitting electrode 703 and the positive receiving electrode. In the capacitor formed by these two electrodes, as shown in FIG. 16B, a current flows at the moment when the rectangular wave voltage source changes from a low potential to a high potential, and thereafter decays with time.

Next, attention is focused on the first transmission electrode 703 and the negative reception electrode. In the capacitor formed by these two electrodes, as shown in FIG. 16C, a current flows at the moment when the rectangular wave voltage source changes from a low potential to a high potential, and thereafter decays with time.
As is well known, the current flowing through the capacitor is proportional to the capacitance of the capacitor. Therefore, similarly to the relationship between FIGS. 6A and 6B, the amplitude of the waveform of the current appearing at the plus side receiving electrode is larger than the amplitude of the waveform of the current appearing at the minus side receiving electrode.
When the current waveform of FIG. 16B and the current waveform of FIG. 16C are converted into currents and the difference is taken by the differential amplifier 307, a voltage waveform as shown in FIG. 16D is obtained.

Further, attention is focused on the second transmission electrode 704, the positive side reception electrode, and the negative side reception electrode.
FIG. 16E shows a waveform of a current flowing through a capacitor formed by the second transmission electrode 704 and the plus-side reception electrode. This is the same as FIG.
FIG. 16F shows a waveform of a current flowing through a capacitor formed by the second transmission electrode 704 and the negative reception electrode. This is the same as FIG.
That is, since the second transmission electrode 704 is arranged symmetrically with the first transmission electrode 703 with respect to the plus-side reception electrode and the minus-side reception electrode, the waveform amplitude is also opposite.
When the current waveform of FIG. 16E and the current waveform of FIG. 16F are converted into currents and the difference is taken by the differential amplifier 307, a voltage waveform as shown in FIG. 16G is obtained. This waveform is a voltage waveform of FIG. 16D in which the voltage polarity is reversed.

  Based on the above, from the differential amplifier 307 when the same waveform signal is given from the rectangular wave voltage source to the first transmission electrode 703 and the second transmission electrode 704 with the finger 402 not approaching the region P1503. The output voltage waveform is the combined waveform of FIG. 16 (d) and FIG. 16 (g). This is FIG. 16 (h). Similarly to the voltage waveform of FIG. 8C, in the state where the finger 402 is not approaching the region P1503, the signals obtained from the electrostatic sensor cells 101 arranged alternately are canceled out and become zero.

Next, consider the waveforms that appear in the electrostatic sensor cell 101 and the differential amplifier 307 when the finger 402 is approaching the region P1503.
Attention is paid to the first transmitting electrode 703 and the positive receiving electrode. In the capacitor formed by these two electrodes, as shown in FIG. 16 (i), a current flows at the moment when the rectangular wave voltage source changes from a low potential to a high potential, and thereafter decays with time.

Next, attention is focused on the first transmission electrode 703 and the negative reception electrode. In the capacitor formed by these two electrodes, as shown in FIG. 16 (j), a current flows at the moment when the rectangular wave voltage source changes from a low potential to a high potential, and thereafter decays with time.
As described with reference to FIGS. 6D and 6E, when the finger 402 comes close to the area P1503, the electrostatic capacitance of the electrostatic sensor cell 101 as viewed from the plus side receiving electrode and the minus side receiving electrode increases. For this reason, the amplitudes of the waveforms in FIGS. 16 (i) and (j) are larger than those in FIGS. 16 (b) and (c), respectively. Further, as described in the above formula, the amplitudes of the waveforms in FIGS. 16 (i) and (j) are almost the same.

  Based on the above, from the differential amplifier 307 when a signal having the same waveform is given from the rectangular wave voltage source to the first transmission electrode 703 and the second transmission electrode 704 with the finger 402 approaching the region P1503. The output voltage waveform is the combined waveform of FIG. 16 (k) and FIG. 16 (g). This is FIG. 16 (l). Similarly to the voltage waveform of FIG. 8E, in the state where the finger 402 is approaching the region P1503, the signals obtained from the electrostatic sensor cells 101 arranged alternately are canceled out because the amplitude of one of them is reduced. First, a signal appears from the differential amplifier 307.

FIG. 17 is an explanatory diagram for explaining the principle of operation for detecting the finger 402.
On the right side of FIG. 17, a voltage waveform whose output timing is shifted by the shift register 1102 that is input to the plurality of transmission electrodes shown on the left side is displayed. The even-numbered voltage waveform is a waveform inverted by the NOT gate 1103.

  At time t1701, a rectangular wave down-edge is applied to the first transmission electrode 1711 and the fourth transmission electrode 1714. Since the first transmission electrode 1711 and the fourth transmission electrode 1714 are not covered with the finger 402, the capacitance does not change. Therefore, the voltage output from the differential amplifier 307 remains zero.

  At time t <b> 1702, a rectangular wave up-edge is applied to the second transmission electrode 1712 and the fifth transmission electrode 1715. The second transmission electrode 1712 is not covered with the finger 402, but the fifth transmission electrode 1715 is covered with the finger 402. Therefore, the electrostatic capacitance of the capacitor formed by the fifth transmission electrode 1715 and the two reception electrodes is not detected. A change in capacity is occurring. Therefore, the voltage output from the differential amplifier 307 is converted to positive.

At time t1703, a rectangular wave down-edge is applied to the third transmission electrode 1713 and the sixth transmission electrode 1716. The third transmission electrode 1713 is not covered with the finger 402, but the sixth transmission electrode 1716 is covered with the finger 402. Therefore, the electrostatic capacitance of the capacitor formed by the sixth transmission electrode 1716 and the two reception electrodes is not detected. A change in capacity is occurring. Therefore, the voltage output from the differential amplifier 307 is converted to positive.
In the following, similar effects overlap.
A waveform of a current generated at each time point is indicated by a dotted line. A composite waveform of this current waveform is shown by a solid line.

As described with reference to FIG. 16, in order to detect the presence of the finger 402 with two electrostatic sensor cells 101 in which two reception electrodes are shared and the transmission conductors 102 are alternately arranged, two transmission electrodes are used. It is necessary to give the signal of the same phase to the conductor 102.
As shown in FIG. 11, each transmission conductor 102 is given a rectangular wave signal shifted by the shift register 1102 at the clock timing. When giving rise and fall of the rectangular wave signal to the two transmission conductors 102, unless one of them is inverted by the NOT gate 1103, signals of the same phase cannot be given to the two transmission conductors 102.

  As can be seen from FIG. 17, in the position detection device 901 of the third embodiment, rectangular waves whose phases are shifted are sequentially applied to the plurality of transmission conductors 102. Since only the half wavelength of the rectangular wave is applied and the rectangular wave is simultaneously applied to the plurality of transmission conductors 102 while shifting the phase, extremely fast position detection can be realized.

[Position detection device using electrostatic sensor cell 101]
FIG. 18 is an explanatory diagram for explaining the principle of operation of the position detection device for detecting the finger 402.
The position detection apparatus of the present embodiment is the same as the embodiment shown in FIG. The difference lies in the signal output from the control unit 1007 and the reception side switch data output from the reception side switch data generation unit 1406.
The reception-side switch data generation unit 1406 is activated by the reset pulse and reception clock pulse generated by the reception-side address counter 1405, generates reception-side switch data, and sends it to the reception switch unit 1004.
The reception-side switch data is a rectangular wave signal that is an integral multiple of a half cycle of the reception clock pulse. The reception-side switch data generation unit 1406 counts a predetermined number of up and down edges of the reception clock pulse from the timing when the reset pulse is input, and maintains the logic true (high potential) state during that time. When the predetermined number is reached, the logic returns to the false (low potential) state, and thereafter the logic false state is maintained until a reset pulse is input again.
In the fourth embodiment, the “predetermined number” of the up and down edges is “3”.
That is, in the position detection device 901 of FIG. 9, the reception switch unit 1004 outputs only one shift register 1202 cell, but in the position detection device of FIG. Two cells of the shift register 1202 output the control signal.

The first receiving electrode 1811 and the second receiving electrode 1812 are simultaneously turned on / off by a first shift register cell (not shown).
The third receiving electrode 1813 and the fourth receiving electrode 1814 are simultaneously turned on / off by a second shift register cell (not shown).
The fifth receiving electrode 1815 and the sixth receiving electrode 1816 are simultaneously turned on / off by a third shift register cell (not shown).
The seventh receiving electrode 1817 and the eighth receiving electrode 1818 are simultaneously turned on / off by a fourth shift register cell (not shown).
The ninth receiving electrode 1819 and the tenth receiving electrode 1820 are simultaneously turned on / off by a fifth shift register cell (not shown).
The first reception electrode 1811, the fourth reception electrode 1814, the fifth reception electrode 1815, the eighth reception electrode 1818, and the ninth reception electrode 1819 are connected to the subsequent analog signal processing unit 1005 as a positive reception electrode.
The second reception electrode 1812, the third reception electrode 1813, the sixth reception electrode 1816, the seventh reception electrode 1817, and the tenth reception electrode 1820 are connected to the subsequent analog signal processing unit 1005 as a negative reception electrode.

Hereinafter, the operation of the position detection apparatus 901 according to the fourth embodiment will be described with reference to FIG.
The reception-side switch data generated from the reception-side switch data generation unit 1406 controls on two adjacent shift register cells. Therefore, at time t1801, the first shift register cell and the second shift register cell output a logical true signal, and the first reception electrode 1811 and the second reception electrode 1812, and the third reception electrode 1813 and the fourth reception electrode. The electrode 1814 is simultaneously turned on.

A combined signal of the first receiving electrode 1811 and the fourth receiving electrode 1814 is output to the analog signal processing unit 1005 through the plus-side output line 1204 (as a signal on the plus-side receiving electrode).
A combined signal of the second reception electrode 1812 and the third reception electrode 1813 is output to the analog signal processing unit 1005 through the negative output line 1205 (as a signal of the negative reception electrode).
At time t1801, the first receiving electrode 1811 to the fourth receiving electrode 1814 are not covered with the finger 402, so that the capacitance of the capacitor does not change and the output waveform does not appear.

At time t1802, the second shift register cell and the third shift register cell output a logical true signal, and the third reception electrode 1813 and the fourth reception electrode 1814, and the fifth reception electrode 1815 and the sixth reception electrode 1816 At the same time, it is turned on.
A combined signal of the fourth reception electrode 1814 and the fifth reception electrode 1815 is output to the analog signal processing unit 1005 through the positive output line 1204 (as a signal of the positive reception electrode).
A combined signal of the third reception electrode 1813 and the sixth reception electrode 1816 is output to the analog signal processing unit 1005 through the negative output line 1205 (as a signal of the negative reception electrode).
At time t1802, the fifth receiving electrode 1815 and the sixth receiving electrode 1816 are covered with the finger 402, so that the capacitance of the capacitor changes, and an output waveform appears.

At time t1803, the third shift register cell and the fourth shift register cell output logic true signals, and the fifth reception electrode 1815 and the sixth reception electrode 1816, and the seventh reception electrode 1817 and the eighth reception electrode 1818 At the same time, it is turned on.
A combined signal of the fifth reception electrode 1815 and the eighth reception electrode 1818 is output to the analog signal processing unit 1005 through the positive output line 1204 (as a signal of the positive reception electrode).
A combined signal of the sixth reception electrode 1816 and the seventh reception electrode 1817 is output to the analog signal processing unit 1005 through the negative output line 1205 (as a signal of the negative reception electrode).
At time t1803, since not only the fifth reception electrode 1815 and the sixth reception electrode 1816 but also the seventh reception electrode 1817 and the eighth reception electrode 1818 are covered with the finger 402, the capacitance of the capacitor changes. An output waveform having an amplitude larger than that at time t1802 appears.

  Compared with the position detection apparatus 901 in FIG. 9, the position detection apparatus in FIG. 18 can obtain a signal waveform with a larger amplitude by obtaining a composite signal of a plurality of reception electrodes.

The following application examples can be considered in the present embodiment.
(1) In order to increase the capacitance of the capacitor formed between the receiving electrode and the transmitting electrode, a pattern in which the receiving electrode is meandered along the land of the transmitting electrode can be formed.
FIG. 19 is a schematic diagram illustrating an example of a wiring pattern of a sensor board.
The land 1902a of the transmission electrode 1902 has a diamond shape, and the reception electrode 1903 is formed to meander the diamond. When the pattern is formed in this manner, the capacitance of the capacitor on the side having the land 1902a can be made larger than the electrostatic sensor cell 101 shown in FIG. The fact that the capacitance of the capacitor on the side with the land 1902a is large means that the capacitance of the capacitor on the side without the land 1902a can be greatly different. That is, the S / N ratio of the electrostatic sensor 1002 is improved, and stronger sensitivity can be obtained.
Further, the shape of the land 1902a is not limited to a rhombus, and application such as a circular shape is also possible.

(2) In order to increase the capacitance of the capacitor formed between the reception electrode and the transmission electrode, it is possible to form a pattern with unevenness between the reception electrode and the land of the transmission electrode.
FIG. 20 is a schematic diagram illustrating an example of a wiring pattern of a sensor board.
The land 2002a of the transmission electrode 2002 is provided with a comb-like cut, and the reception electrode 2003 is provided with a protrusion facing the cut. When the pattern is formed in this way, the capacitance of the capacitor on the side having the land 2002a can be made larger than that of the electrostatic sensor cell 101 shown in FIG.
The wiring pattern of FIG. 20 also has the same effect as that of FIG. 19, that is, the S / N ratio of the electrostatic sensor 1002 is improved, and stronger sensitivity can be obtained.

  The reception electrode 1903 in FIG. 19 and the reception electrode 2003 in FIG. 20 described in the above (1) and (2) are the same as the first reception electrode and the second reception electrode described in FIGS. There is no symmetrical relationship about the line between the first receiving electrode and the second receiving electrode. Rather, it can be understood that there is a rotationally symmetric relationship around the midpoint of the common first receiving electrode and second receiving electrode constituting two electrostatic sensor cells.

  Note that the receiving electrode 1903 in FIG. 19 and the receiving electrode 2003 in FIG. 20 described in the above (1) and (2) are the first receiving electrode and the second receiving electrode described in FIGS. It is not a receiving electrode formed in a straight line. For this reason, the symmetry of a receiving electrode cannot be ensured with a single electrostatic sensor cell. That is, when a reception electrode having a special shape such as the reception electrode 1903 in FIG. 19 or the reception electrode 2003 in FIG. 20 is employed, it is necessary to combine two electrostatic sensor cells in order to maintain the object of rotation.

In the present embodiment, an electrostatic sensor cell, an electrostatic switch that is an assembly of the electrostatic sensor cell, and a position detection device to which the electrostatic switch is applied have been disclosed.
In the electrostatic sensor cell of this embodiment, the two receiving electrodes are completely symmetrical. For this reason, since the adjustment of dimensions and the like when mounting the sensor on the substrate can be performed very simply, the effect of canceling the common-mode noise when the differential amplifier is connected can be exhibited to the maximum.
Furthermore, the electrostatic sensor cell of this embodiment is provided with a land that is close to the side of one receiving electrode of one transmitting electrode. For this reason, when one transmission electrode is seen from a differential amplifier, it is asymmetrical shape. Therefore, when the differential amplifier is connected, it is possible to reliably detect whether or not the finger is close without losing the effect of canceling the common-mode noise.

  In the electrostatic switch of this embodiment, the above-described electrostatic sensor cell has two reception electrodes in common, and two transmission electrodes and lands are alternately provided. When viewed from the receiving electrode side, the asymmetrical transmitting electrodes are arranged in two symmetry. For this reason, when the finger is not approaching, signals derived from the asymmetric shape of the transmission electrode cancel each other, so that no signal appears in the differential amplifier. That is, the detection signal is kept in an equilibrium state. When a finger is brought close to one electrostatic sensor cell, this equilibrium state is lost and a signal appears in the differential amplifier. Therefore, when the finger is not approaching, it is in the “zero” state, and when the finger is approaching, it is in the “non-zero” state. Therefore, the logic is clearer and more reliable than when using a single electrostatic sensor cell. Can be output. That is, an electrostatic switch resistant to noise can be realized.

In the position detection device of this embodiment, the above-described electrostatic sensor cell is developed vertically and horizontally on a sensor substrate. Then, a one-shot pulse that is an integral multiple of a half cycle of the clock pulse is sequentially applied to the transmission electrode with a phase delayed by a half cycle unit of the clock pulse. At that time, the transmission switch unit is configured such that a NOT gate is interposed by skipping one and a rising or falling edge is simultaneously applied to one reception electrode from two transmission electrodes.
With the above configuration, it is possible to provide a practical position detection device that applies a noise-resistant electrostatic switch, has a simple circuit configuration, is resistant to noise, and has a high scanning speed.

  The embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and other modifications may be made without departing from the gist of the present invention described in the claims. Includes application examples.

  DESCRIPTION OF SYMBOLS 101 ... Electrostatic sensor cell, 102 ... Transmission conductor, 103 ... Reception electrode, 202 ... Insulation sheet, 203 ... Protection sheet, 301 ... Electrostatic switch, 302 ... Signal source, R303 ... Resistance, R304 ... Resistance, 305 ... Operational amplifier, 306 Operational amplifier 307 Differential amplifier 308 Electrostatic sensor unit 309 Multiplier 310 LPF 310 Low pass filter 311 Comparator 402 Finger Cm1 Capacitor Cma Capacitor Cp1 Capacitor Cpa: capacitor, 701: electrostatic switch, 702: electrostatic sensor unit, 703 ... first transmission electrode, 704 ... second transmission electrode, 901 ... position detection device, 902 ... position detection plane, 1002 ... electrostatic sensor, 1003 ... Transmission switch unit, 1004 ... Reception switch unit, 1005 ... Analog signal processing unit, 006 ... A / D converter, 1007 ... control unit, 1008 ... transmission electrode, 1102 ... shift register, 1102a ... bit cell, 1103 ... NOT gate, 1105 ... analog signal processing unit, 1105a ... current voltage conversion unit, 1105b ... current voltage Conversion unit 1202 ... Shift register, 1202a ... Bit cell, 1203 ... Analog switch, 1203a ... Switch, 1204 ... Positive output line, 1205 ... Negative output line, 1206 ... Positive output line, 1302 ... LPF, 1402 ... Clock generation , 1403 ... transmission side address counter, 1404 ... transmission side switch data generation unit, 1405 ... reception side address counter, 1406 ... reception side switch data generation unit, 1407 ... buffer memory, 1408 ... centroid calculation unit, 1502 ... rectangular wave Signal source, 1711 ... first transmission electrode, 1712 ... second transmission electrode, 1713 ... third transmission electrode, 1714 ... fourth transmission electrode, 1715 ... fifth transmission electrode, 1716 ... sixth transmission electrode, 1811 ... first reception Electrode, 1812 ... second receiver electrode, 1813 ... third receiver electrode, 1814 ... fourth receiver electrode, 1815 ... fifth receiver electrode, 1816 ... sixth receiver electrode, 1817 ... seventh receiver electrode, 1818 ... eighth receiver electrode , 1819 ... ninth reception electrode, 1820 ... tenth reception electrode, 1902 ... transmission electrode, 1902a ... land, 1903 ... reception electrode, 2002 ... transmission electrode, 2002a ... land, 2003 ... reception electrode

Claims (6)

A plurality of conductor patterns having a predetermined number of land portions are arranged in the first direction, and at least two conductors are in the second direction intersecting the first direction and in the vicinity of the land portions. A sensor in which the pattern is electrically insulated from the conductor pattern having the land portion in proximity to each other;
A signal supply circuit for supplying a predetermined signal to the conductor pattern arranged in the first direction;
A signal detection circuit having a differential amplifier circuit for supplying a signal from the two conductor patterns arranged in the second direction and generating a differential signal of the two;
The position of the indicator on the sensor is obtained based on a change in electrostatic coupling between the conductor pattern arranged in the first direction and the conductor arranged in the second direction. ,
Position detection device. A transmission conductor selection circuit for selectively supplying a signal output from the signal supply circuit to the at least two conductor patterns;
The position detection device according to claim 1. A receiving conductor selection circuit for supplying a signal from the conductor pattern arranged in the second direction to the differential amplifier circuit;
The position detection device according to claim 2. The conductor pattern arranged in the second direction has a predetermined pattern shape,
The position detection device according to claim 2. The conductor pattern arranged in the second direction is formed in a shape that circulates at least a part of the outer periphery of the land portion,
The position detection device according to claim 3. A plurality of conductor patterns having a predetermined number of land portions are arranged in the first direction as conductors for signal transmission,
In a second direction intersecting the first direction, at least two conductor patterns are arranged in the vicinity of the land portion and are electrically insulated from the conductor pattern having the land portion. The conductor pattern is arranged as a signal receiving conductor,
Electrostatic sensor.